Athina Helene Onassis Roussel (born January 29, 1985) is a French-Greek heiress, the only surviving descendant of Greek shipping magnate Aristotle Onassis, and the sole heir of Aristotle's daughter Christina Onassis, who inherited 55% of his fortune. The remaining 45%, minus the $26 million left to Onassis' widow Jacqueline Kennedy Onassis, was left to the Alexander S. Onassis Public Benefit Foundation, established in honor of Aristotle's late son, and Athina's uncle. The two halves of the fortune are separately managed. Despite keen investigation by the media, the extent of Onassis de Miranda's wealth remains unknown.
Onassis married Brazilian Olympic showjumper Álvaro de Miranda Neto in 2005. She is a competitive show jumper in her own right, under the name Athina Onassis de Miranda, until her divorce in 2016.